In a recent trend of high performance and downsizing of an electronic device, a high density and a high function of a circuit component are further required. In view of the above, also in a module to which a circuit component is mounted, it is required to seek for a high density and a high function. In order to cope with such a requirement, the multilayering of a wiring board is often performed at present.
In such a multilayer wiring board as described above, a plurality of wiring patterns are disposed to be separated from one another and to be almost parallel, a plurality of insulating members are each provided between the corresponding ones of the wiring patterns, an electronic component such as a semiconductor component is embedded in one or some of the insulating members in a manner to be electrically connected to at least one of the wiring patterns, and a plurality of interlayer connection bodies (vias) penetrating through the insulating members in a thickness direction are formed, so that the wiring patterns are electrically connected to one another (for example, see Reference 1).
On the other hand, with regard to a voltage conversion IC, in order to make the voltage conversion IC drive sufficiently, the voltage conversion IC is configured such that a first capacitor is disposed in parallel to the voltage conversion IC in an input side, a smoothing inductor is disposed in an output side to be connected in series to the voltage conversion IC, the other terminal of the smoothing inductor is connected to an output terminal of a module, and a second capacitor is disposed to be connected in parallel. The first capacitor has a capacitance of about 2 μF and is used mainly for the stabilization of an input voltage to the voltage conversion IC. The second capacitor has a capacitance of about 4 μF and is used together with the smoothing inductor mainly for the stabilization of an output voltage from the voltage conversion IC.
The first capacitor has a size of 1 mm×0.5 mm for example, while the second capacitor has a size of 1.6 mm×0.8 mm for example. Further, the smoothing inductor has a size of 2 mm×1.25 mm for example.
Accordingly, for building in the voltage conversion IC as described above in the multilayer wiring board as an electric component, it is necessary to build in the capacitors and the inductor described above together with the voltage conversion IC. However, as described above, the first capacitor, the second capacitor, and the inductor are comparatively large in size and are thick, and thus it is difficult to build in all of the voltage conversion IC, the capacitors, and so on in the multilayer wiring board.
Thus, Reference 2 discloses to fabricate a module similar to a module in a case where electronic components such as a semiconductor component and so on are built in, by adopting a configuration where only a voltage conversion IC is built in a multilayer wiring board and where a first capacitor, a second capacitor, and an inductor are disposed in a capacitor built-in layer formed on the multilayer wiring board.
However, in Reference 2, the arrangement of the first capacitor, the second capacitor, and the inductor formed on the multilayer board is not taught at all. Accordingly, a large noise is overlapped on an input voltage depending on the arrangement state of the first capacitor, the second capacitor, and the inductor, thereby causing a problem that a stable output voltage cannot be obtained.